1. Field of the Invention
The present invention relates to a format determining apparatus, and more particularly to a format determining apparatus that determines a format of data recorded on an optical disk.
2. Description of the Related Art
Some optical disk reproducing apparatuses represented by a CD (Compact Disk) player can reproduce data in a CD-DA (Compact Disk Digital Audio) format as well as data in a CD-ROM (Compact Disk Read Only Memory) format. The above-described optical disk reproducing apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-77221 (Patent Literature 1).
The above-described optical disk reproducing apparatus includes a signal processing unit for reproducing CD-DA format data as well as a CD-ROM decoder. Suppose that data at a physical position specified by a predetermined subcode address on a loaded optical disk is read by a pick-up. When the read data is in the CD-DA format, the optical disk reproducing apparatus converts main data decoded by the signal processing unit to an analog signal, and then outputs the same outside. On the other hand, when the data at the physical position specified by the subcode address is in the CD-ROM format, the optical disk reproducing apparatus further decodes, by the CD-ROM decoder, a digital signal decoded by the signal processing unit, and outputs the same outside.
In short, the optical disk reproducing apparatus including the CD-ROM decoder executes different types of processing between when the data recorded on the optical disk is in the CD-DA format, and when the data is in the CD-ROM format. Accordingly, when the data of the optical disk is reproduced, the format (CD-DA or CD-ROM) of the data needs to be specified.
The optical disk reproducing apparatus disclosed in Japanese Patent Application Laid-Open No. 2003-77221 determines whether or not the data decoded by the CD-ROM decoder includes a sync signal. Although the sync signal is included in the data in the CD-ROM format, it is not included in the data in the CD-DA format. Accordingly, the format of the data can be determined.
As a result of the above-described determination based on sync signal, when the decoded data does not include the sync signal, the data is determined not to be in the CD-ROM format. In this case, however, it is unclear whether the data is in the CD-DA format or the pick-up has failed in the generation of a reproduction signal for some reason. Thus, in the conventional optical disk reproducing apparatus, when the decoded data is not in the CD-ROM format, the above-described determination processing is repeated a plurality of times in view of the case where the pick-up has failed in the generation of the reproduction signal. It requires some time.